Automotive compressor

ABSTRACT

An automotive compressor is provided having a casing defining an intake section for fluid for compression, and a delivery section for delivering the compressed fluid. An impeller is movable angularly inside the casing to increase the pressure of the fluid. A distributor is carried by the intake section of the casing to conduct the fluid for compression to the impeller. The casing and the distributor are defined by separate members connected releasably to each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of European Patent Application No.04425351.6, filed on May 18, 2004, the subject matter of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an automotive compressor, in particularfor supplying pressurized fluid to fuel cell systems.

Automotive centrifugal compressors are known which substantiallycomprise a fixed portion, and one or more bladed impellers driven by anexternal motor. The fixed portion is normally defined by a hollowcasing, in which the impeller rotates to produce the desired compressionof the fluid flowing through it.

More specifically, the casing defines, integrally, an intake sectionthrough which the fluid to be compressed is fed to the impeller toincrease its kinetic energy; and a delivery section defined by adiffuser, in which the kinetic energy is converted to pressure energy.

The intake section may have a number of fixed blades acting as adistributor, i.e. defining respective channels of given shape to conductand accelerate the fluid intake onto the impeller in the desireddirection of impact on the impeller blades.

In other words, the fixed blades substantially provide for imparting tothe fluid for compression an optimum direction of impact on the movableblades of the impeller, so as to reduce fluid-dynamic losses and improvethe overall efficiency of the compressor.

Fuel cell drive systems require compressor impellers of variablegeometry, both for test purposes and to permit a certain amount offlexibility in the equipping of different types of vehicles.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an automotivecompressor designed to permit such flexibility in a straightforward,low-cost manner.

According to the present invention, there is provided an automotivecompressor comprising: a casing defining an intake section for a fluidfor compression, and a delivery section for delivering the compressedfluid; an impeller movable angularly inside said casing to increase thepressure of said fluid; and a distributor carried by said intake sectionof said casing to conduct the fluid for compression to said impeller;wherein said casing and said distributor are defined by separate membersconnected releasably to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred, non-limiting embodiment of the present invention will bedescribed by way of example with reference to the accompanying drawings,in which:

FIG. 1 shows a partly sectioned view in perspective of a compressor inaccordance with the present invention;

FIG. 2 shows a view in perspective, with parts removed for clarity, of adetail of the FIG. 1 compressor.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 and 2, number 1 indicates as a whole acompressor, of axis A, substantially comprising a fixed portion 2, andan impeller 3 housed inside fixed portion 2 and rotated about axis A bya known drive system 4 (shown only partly in FIG. 1) to increase thepressure of the fluid flowing through compressor 1.

In the following disclosure, drive system 4 is described only asrequired for a clear understanding of the present invention. Morespecifically, of drive system 4, FIG. 1 shows only a housing 5, and anoutput shaft 6 having an end portion 7 outside housing 5 and connectedto impeller 3 as decribed in detail below.

Fixed portion 2 substantially comprises a casing 8 defining a throughaxial cavity housing impeller 3.

Casing 8 comprises a minimum-diameter axial end portion 10 defining anintake section 11 for the fluid for compression; a maximum-diameteropposite axial end portion 12 fixed in conventional manner, e.g. byscrews not shown, to a flange 13 integral with housing 5 of drive system4; and an intermediate portion 14 connecting axial end portions 10 and12, and defining a screw diffuser 15 extending circumferentially withrespect to axis A to deliver the compressed fluid.

Impeller 3 is housed substantially in intermediate portion 14 of casing8, is fitted to portion 7 of shaft 6 of drive system 4 projecting fromhousing 5, and comprises a number of substantially radial blades 16equally spaced about axis A.

More specifically, impeller 3 has a through axial hole 17 engaged byportion 7 of shaft 6 of drive system 4, and is gripped axially between ashoulder 20 of portion 7, adjacent to drive system 4, and a nut 21screwed to a threaded free end of portion 7.

When tightened, nut 21 makes impeller 3 integral both axially andangularly with portion 7 of shaft 6 of drive system 4; and impeller 3 isremoved by simply unscrewing nut 21 completely and withdrawing impeller3 axially off portion 7 of shaft 6.

An important aspect of the present invention is that fixed portion 2 ofcompressor 1 also comprises a distributor 22 formed separately from andfitted releasably to casing 8.

Distributor 22 provides for conducting and accelerating the fluid forcompression towards impeller 3, and substantially comprises a shapedcentral portion 23; an outer tubular portion 24 surrounding and spacedradially apart from central portion 23; and a number of blades 25radiating generally between central portion 23 and tubular portion 24.

Distributor 22 is housed inside a cylindrical seat 26 formed in axialend portion 10 of casing 8. More specifically, seat 26 is boundedtowards impeller 3 by an annular shoulder 27 defining an axial stop fortubular portion 24 of distributor 22. In the example shown, distributor22 is housed interferentially inside seat 26 of casing 8, though otherreleasable retaining systems may obviously be used.

Blades 25 define a number of conducting channels for imparting to theflow entering compressor 1 an appropriate direction with respect toblades 16 of impeller 3.

Central portion 23 is advantageously ogival, increasing in diametertowards impeller 3, so as to gradually reduce the section of the variouschannels defined by blades 25 in the flow direction.

Central portion 23 also comprises, on the side facing impeller 3, anaxial cavity 28 loosely housing the free end of portion 7 of shaft 6 andrelative nut 21.

The advantages of compressor 1 according to the present invention willbe clear from the foregoing description.

In particular, impellers 3 of different designs can be used on the samecompressor 1, and operation of the compressor within a given flow rangecan be optimized with no need to replace the whole of fixed portion 2,but simply by using different distributors 22 suited to differentimpellers 3, i.e. having a geometry of fixed blades 25 suited to that ofmovable blades 16 to minimize fluid-dynamic losses.

Distributor 22 may be produced using methods and materials best suitedto the operating conditions and function involved.

Fixed blades 25 of distributor 22 also support ogival central portion 23to improve fluid-dynamic performance as a whole.

A highly flexible compressor 1 for different types of applications andvehicles is thus obtained relatively simply, with no reduction inefficiency. On the contrary, operation of compressor 1 is optimizedusing different impellers 3.

Clearly, changes may be made to compressor 1 as described andillustrated herein without, however, departing from the scope of theaccompanying claims.

The invention has been described in detail with respect to preferredembodiments, and it will now be apparent from the foregoing to thoseskilled in the art, that changes and modifications may be made withoutdeparting from the invention in its broader aspects, and the invention,therefore, as defined in the appended claims, is intended to cover allsuch changes and modifications that fall within the true spirit of theinvention.

1. An automotive compressor comprising: a casing defining an intakesection for a fluid for compression, and a delivery section fordelivering the compressed fluid; an impeller movable angularly insidesaid casing to increase the pressure of said fluid; and distributingmeans carried by said intake section of said casing for conducting thefluid for compression to said impeller; wherein said casing and saiddistributing means are defined by separate members connected releasablyto each other.
 2. A compressor as claimed in claim 1, wherein saidintake section of said casing defines a seat for said distributingmeans.
 3. A compressor as claimed in claim 2, wherein said distributingmeans is housed interferentially inside said seat of said casing.
 4. Acompressor as claimed in claim 1, wherein said distributing meanscomprises, integrally, a central portion; a tubular portion surroundingand spaced radially apart from said central portion; and a number ofblades radiating generally between said central portion and said tubularportion.
 5. A compressor as claimed in claim 4, wherein said centralportion is ogival, increasing in diameter toward said impeller.
 6. Acompressor as claimed in claim 5, wherein the said central portionincludes an axial cavity on the side facing the impeller.
 7. Acompressor as claimed in claim 6, wherein said impeller has a throughaxial hole for receiving a shaft of a drive system, the shaft having afree end for receiving a nut for holding the impeller in place, andwherein the axial cavity of said central portion of said distributor isshaped to loosely house the free end of the shaft and the nut.
 8. Anautomotive compressor comprising: a casing defining an intake sectionfor a fluid for compression, and a delivery section for delivering thecompressed fluid; an impeller movable angularly inside said casing toincrease the pressure of said fluid; and a distributor carried by saidintake section of said casing to conduct the fluid for compression tosaid impeller; wherein said casing and said distributor are defined byseparate members connected releasably to each other.
 9. A compressor asclaimed in claim 8, wherein said intake section of said casing defines aseat for said distributor.
 10. A compressor as claimed in claim 9,wherein said distributor is housed interferentially inside said seat ofsaid casing.
 11. A compressor as claimed in claim 8, wherein saiddistributor comprises, integrally, a central portion; a tubular portionsurrounding and spaced radially apart from said central portion; and anumber of blades radiating generally between said central portion andsaid tubular portion.
 12. A compressor as claimed in claim 11, whereinsaid central portion is ogival, increasing in diameter toward saidimpeller.
 13. A compressor as claimed in claim 12, wherein the saidcentral portion includes an axial cavity on the side facing theimpeller.
 14. A compressor as claimed in claim 13, wherein said impellerhas a through axial hole for receiving a shaft of a drive system, theshaft having a free end for receiving a nut for holding the impeller inplace, and wherein the axial cavity of said central portion of saiddistributor is shaped to loosely house the free end of the shaft and thenut.